That, in a sense, was always the point. Before mechanical refrigeration, country houses relied on these subterranean chambers to store ice harvested from nearby lakes and ponds through the winter months; the surrounding earth acted as insulation, keeping the interior cold well into summer. Most visitors walking the estate today would have no reason to suspect what lies beneath the trees.

The structure itself is circular and brick-built, with a cut stone manhole set into its roof. There is no trace of a side entrance, which would have been the more common arrangement in many Irish icehouses, used to pack ice in and extract it later. Instead, everything passed through the top. A description of the chamber captures the ingenuity of the design: near the ridge into which the icehouse has been cut, a depression in the ground conceals a grille set over an aperture in the masonry roof. Beneath the grille, a rectangular hole with tapered sides was shaped to accept a close-fitting plug, keeping cold air sealed inside. The icehouse is shown on the 1837 edition of the Ordnance Survey six-inch map, where it appears immediately to the west of a lake that has since been reduced in size. It does not appear on later editions, suggesting it had fallen out of use or simply ceased to be considered worth recording. By that point it would have been little more than a mound beside a shrunken lake, which is more or less what it remains today.

The structure sits roughly 990 metres to the south of the main house, now known as Tullynally Castle, with a pathway running about 85 metres to its west. The lake that once lay just beside it is still there, diminished. The icehouse itself is not marked on modern maps, and its setting within dense conifers means it offers no obvious signals of what it is.